Novel Polishing Process to Fabricate Ultra Low Thickness Variation Diamond Substrates for Next Generation Beam Tracking Detectors

Diamond crystals with small total thickness variation (TTV) and local thickness variation (LTV) values are needed for position sensitive fast particle detectors for particle tracking/timing, and detecting direct/indirect beams. The fabrication of ultra-flat, low surface defectivity diamond detectors represents a major technological challenge. Although current commercial technology can produce 100m thick, high quality diamond crystals, the current state-of-the- art polishing methods are unable to polish diamond crystals with low thickness variation (typically lesser than few microns). Sinmat has developed a novel reactive chemical mechanical polishing (RCMP) process to polish, planarized, and flatten diamond crystals free of surface/subsurface defects. By combining this RCMP process with special engineered sample holders, ultra-low TTV and LTV surfaces can be fabricated (with TTV lesser than 1 micron) for high performance detector applications. In the Phase I part of the project, Sinmat had demonstrated ultra flat diamond crystals with surfaces free of damage and scratches. By combining the RCMP process and special samples holders, we were able to achieve ultra-flat surfaces. Such RCMP polished diamond crystals have shown excellent detector performance with 3X increase in pulse height. In the Phase II effort, the RCMP process will be further optimized to achieve ultra low TTV diamond crystal detectors for beam tracking applications at FRIB- NSCL facilities. Commercial Application and Other Benefits: The ability to achieve ultra-flat and defect free diamond crystals will be very beneficial for several applications in the fields of nuclear instrumentation, nuclear radiators, X-ray optics, and next generation electronics. Such devices will help in improving detection systems, instrumentation, and various techniques used in nuclear physics. Such engineered ultra-smooth diamond substrates could also be used for heat dissipation in silicon based electronics.